We introduce a new technology for Manufactureable, High Power Density, High Volume Utilization Nuclear Batteries. Betavoltaic batteries are an excellent choice for battery applications which require long life, high power density, or the ability to operate in harsh environments. In order to optimize the performance of betavoltaic batteries for these applications or any other application, it is desirable to maximize the efficiency of beta particle energy conversion into power, while at the same time increasing the power density of an overall device. Increasing power density is a difficult problem because, while both the active area of the semiconductor used for the beta energy conversion and the layer of radioisotope that provides the betas for this conversion are very thin (100's of nanometers), the thickness of the substrate supporting the radioisotope layer and the overall thickness of the semiconductor device wafers are on the order of 100's of microns.
In another embodiment for this technology, there are several technical constraints that must be considered when designing a low cost, manufacturable, high volume, high power density silicon carbide (SiC) betavoltaic device. First, consideration must be given to the energy profile of radioisotopes to be used, and the volume at which such material can be produced. For example, tritium is one of the several viable radioisotope candidates, since it can be produced in sufficient quantities to support high volume device manufacture, and its energy profile fits well with a range of power generation design parameters.
Secondly, in order to produce high power density in betavoltaics, a large device surface area is required. There are issued and pending betavoltaic patents that mention patterning methods for pillars, pores or other structures which yield such high surface area—patent application Ser. No. 11/509,323 is an example, and can be used as a reference for pillared betavoltaic device construction. These methods must be optimized appropriately in order to meet fabrication objectives, while controlling costs.
Thirdly, SiC has been shown to be the ideal material for betavoltaic devices, e.g. see reference patent application Ser. No. 11/509,323. However, SiC has unique processing, fabrication and design requirements which must be met in order to produce a workable device. For example, fabrication of SiC devices requires high temperature epitaxial processes. Because of such high temperature requirements, these epitaxial processes add an element of complexity and cost, not seen with processes relating to other semiconductors, such as Si, and must be taken into account accordingly, or fabrication techniques must be developed to remove such complex and costly processes entirely.
Fourthly, it is desirable to integrate betavoltaic devices directly with Silicon (Si)-based electronics, including, but not limited to, microprocessor and memory devices. Thus, there is a need for designs and fabrication processes which anticipate such integration.
Devices which address or anticipate the aforementioned design considerations are disclosed in this current or co-pending applications, as mentioned above. Methods for fabricating same are also disclosed.